With this Major Instruments Proposal Applications we request funds to purchase a Beckman Optima XL-I Analytical Ultracentrifuge and an Affinity Sensors IAsys Optical Biosensor Apparatus, to be used to upgrade and complete our armamentarium of physical biochemical equipment for the characterization of the structure and interactions of macromolecular complexes of biological importance. Six major research groups within the Institute of Molecular Biology at the University of Oregon have described specific projects that will be greatly facilitated by these items of equipment. The laboratories and research projects that have been proposed specifically are listed as follows: Peter von Hippel laboratory (Assembly and Regulatory Reactions in Replication and Transcription); Frederick Dahlquist laboratory (The Energetics of Assembly of the Bacterial Chemotaxis Signaling Complex); Tom Stevens laboratory (The Role of SNARE Proteins in Controlling the Specificity of Membrane Fusion in Yeast); Carlos Bustamante laboratory (Assembly and Structure of Phage and Transcription Complexes); Diane Hawley laboratory (Assembly and Function of the RNA polymerase II Transcription Complexes); and Gregory Flynn laboratory (Hsp70 Chaperones and Their Role in Protein Folding). In addition, other members of the Institute of Molecular Biology will use the requested equipment as their research projects become amenable to biophysical characterization.